Bowl Gouge Flute Descriptors

[Neil S]

Bowl Gouge Flute Descriptors - Part 1 of 8

Warning: Long multi-post starter to this thread… and some folk may prefer to be spending their time out in their workshop turning wood than engaging in pedantic stuff about flute profiles and names… :~}

I have become concerned about the sloppy and growing misuse of some bowl gouge flute descriptors and my focus in this thread is entirely on those descriptors in order to reduce the confusion that I’m seeing over their use in our woodturning community.

It is not my intention in this thread to discuss my or your preferences for one flute profile over another or which flute profile might be better suited to a particular grind or use. There have and will be many other threads for that.

Let’s keep this thread to a discussion on just the bowl gouge flute descriptors.

–o0o–​

Because of the limits on photo attachments I will cover the following in separate posts:

Part 1 Intro and Elliptical
Part 2 Catenary or Parabolic
Part 3 Examples of Parabolic Flutes
Part 4 Other Examples of Parabolics
Part 5 The Vs and Us
Part 6 Other Examples in the V Flute Tradition
Part 7 A Few side by side Comparisons
Part 8 The Importance of Accurate Descriptors


Elliptical

Back in the early 70s when I began woodturning the flutes on bowl gouges had simple names like shallow and deep, which were easily understood. I can’t recall anyone giving the flute on the deep bowl gouges any other descriptor than that, but looking at the flute on the forged bowl gouge that Peter Child included in his 1970s book it might have been called elliptical…

​

And here is how Roy Child (Peter Child’s son) drew that elliptical flute profile that they were using back then in his later 1999 article http://www.peterchild.co.uk/info1/sflute.htm

​

There was then a period when elliptical was more widely used to describe a flute profile that had a continuously changing curve and Henry Taylor Tools described the gouge that they made to Roy Child’s design as having an “elliptical flute cross section”, which they called the SuperFlute. The ellipse is a precise mathematical curve derived from Conics and where a flute is elliptical it would be appropriate to call it that, but few are.

Here is how an elliptical flute would look in a round bar…

​

Roy Child himself neither named his flute design the SuperFlute nor described it as elliptical. In his own words he simply described it as follows, “it has a large radius at the sides blending into a small radius at the bottom of the flute.” Here is a diagram drawn by Roy of his flute profile design alongside the SuperFlute made for him by Henry Taylor Tools…

​

So, as can be seen, the SuperFlute is neither a true ellipse (as specified in Conics) nor is it a parabola (more on those later), although it is much closer to a parabola than some bowl gouge flute profiles that have been described as parabolic. It is in fact closest to the catenary profile as seen in the example of a chain suspended from two level points or arches like the St Louis Arch that might be seen by some of you on your side of the pond.

 

[Neil S]

Part 2 Catenary or Parabolic

There are only small differences between the catenary and parabolic curves. For comparison, here are those two curves superimposed on one another, the parabolic in red and catenary in black…

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For the purposes of woodturners they are close enough to be used interchangeably, however, catenary is not a term in common use and there is already too much confusion around parabolic as a descriptor to muddy the waters any further by introducing another descriptor. By default parabolic has become the descriptor for flute profiles that are close to either catenary or parabolic. Relevant to the distinction between those two and the V profile are the continuous curves in the upper sides of their flutes. This is more obvious in the catenary and, although the upper sides of a parabolic flute start to straighten out, they never become fully straight as they do in a V flute.

The Parabola is a curve that is derived from Conics and, although very precise in its parameters, it can have many manifestations, eg….

​

What we see on bowl gouges is a flute that is usually closer to the middle curve in the one shown above. As can be seen, the curve is continuous and the sides never become straight.

 

[Neil S]

Part 3 Examples of Parabolic Flutes

When David Ellsworth developed his signature bowl gouge in the early 1980s he and/or Crown used the term parabolic to describe his flute profile. Like most flutes that are called parabolic, it’s not quite a true parabola, but close enough. Here it is with the characteristic continuous curve that runs right up the sides …

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Some other bowl gouges that subsequently came along with parabolic or close to parabolic flutes have been Woodcut (left) and Vicmarc (right)…

​

 

[Neil S]

Part 4 Other Examples of Parabolics

Here are a few more examples of parabolics that I don’t have myself for which I have been able to find clear end view images on the web …

Ashley Harwood


Glenn Lucas (Hamlet)


Robust


Oneway Mastercut
(coutesy of John Kananis)​

Forum members may have images of other examples of bowl gouges with parabolic flutes that I don’t have that they might like to post here with a clear end view of the flute profile, eg Hamlet Masterflute and Robust parabolic.

 

[Neil S]

Part 5 The 'V's and 'U's

That brings us down (or back) to the V and U profiles. The U fluted profile is as old as spindle roughing gouges (not they are intended for bowl work), which is semi-circular at the bottom of the flute with straight parallel sides. Here is the ¾” D-way U Fluted BG…

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When the straight sides are at an angle to each other the now well established and understood convention is to call it a V flute. The size of the circular section in the bottom of the flute and the angle of the straight sides to one another can vary…

​

This flute profile came in with making bowl gouges from HSS bar and their profiles were partly influenced by the milling cutters and grinding wheels available and the economics of the profiles that can be readily achieved with those. Most of us that had an early HSS bowl gouge are familiar with the V profile. For example, here is my early P&N V flute profile…

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Jerry Glaser, who pioneered the use of HSS gouges in the mid-1960s, and later the high alloy powdered metals, used a V profile as one of his preferred flute designs. Doug Thompson who followed, acknowledges Jerry as his predecessor with his V flute design. Theirs is a more open V that most of us are now familiar with…

Thompson V flute​

 

[Neil S]

Part 6 Other Examples in the V Flute Tradition

Among the other excellent (IMO) bowl gouges in the V fluted bowl gouge tradition are the D-way (next image) and Jamieson (the image below that), which to my eye are very similar with both having wider and deeper cut circular sections at the bottom of their V flutes…

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Despite some wording to the contrary on their websites, neither gouge is parabolic in any way that I can see, no matter how hard I squint… :~}

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This is not a criticism of the excellent bowl gouges from these two woodturning tool designers/makers. As I have said here and elsewhere, they both have 1st rate V fluted bowl gouges, however, I just can’t see a parabolic profile on any of the gouges that I have from them.

Are there any other bowl gouges in the same esteemed V fluted tradition?

 

[Neil S]

Part 7 A Few side by side Comparisons

Here are a few side by side comparisons to highlight the differences between V and parabolic flute profiles…

From left Thompson V, Jamieson V &
Henry Taylor parabolic


Ellsworth sig parabolic on left
P&N V on right


P&N V on left & Thompson V on right


Thompson V on left &
D-way V on right​

 

[Neil S]

Part 8 The Importance of Accurate Descriptors

Back before we could purchase our gouges online we would go to shops or events that had vendor stalls to select our tools. We could inspect them before we bought them.

Nowadays most of us buy our tools online and we are dependent on accurate information on websites to inform our purchasing decisions. Likewise, it’s important that we don’t create confusion in what the established descriptors mean.

I reckon that three simple descriptors is all we need to avoid confusion; U, V & Parabolic. The last being preserved for flutes that have a continuous curve even where they are not a precise parabola. In addition to the catchy and meaningless names given to some, the makers of the parabolics can add wording to that descriptor to explain and extol the features and virtues of their flutes.

Any bowl gouge flutes that have straight sides are either U or V flutes. If it is a V flute, the makers can add any manner of words to that descriptor to explain and extol the features and virtues of their particular flute design (other than parabolic .

~~o0o~~

I welcome any corrections, other perspectives, examples, inputs or critiques.

As stated in my first post, it is not my intention in this thread to discuss my or your preferences for one flute profile over another or which flute profile might be better suited to a particular grind or use. There have and will be many other threads for that.

Let’s keep this thread to a discussion on just the bowl gouge flute descriptors.


Letting those who are members of other woodturning forums know that I have or intend to post this thread elsewhere.​

 

[Kirk Amidon]

You put a lot of work into that Neil. Thanks a bunch. Lot of good nuances shown.

 

[Kevin Jenness]

A great example of the saying "A picture is worth a thousand words." If the vendors would provide clear photos of their flute shapes it would be simpler.

 

[hockenbery]

Great overview.
maybe an article for the AAW journal …
when I took Ellsworth’s class in 1995 we use the Henry Taylor super flute tools. People were calling it parabolic.
the main identifier is the curve in the flute wall. I’ve been using the Ellsworth grind since then and am pretty good with it.

the best tool I have used with the Ellsworth grind is the Jamison gouge. for me it performs the flute up shear cut with the leading edge of the wing more Smoothly than any tool I have used.
you call it a vee. Jamieson calls it parabolic. Your diagram confirms vee.
I also heard (reliable source rumor.) that Thompson makes the Jamieson gouge by grinding his 3/4” vee flute in the 5/8” bar..

oddly the 5/8 bar vee from Thompson performed poorly for me with the Ellsworth grind so mine now has the 40/40 and is a nice tool to use with that grind.

the wider flute on the jaimson vee must be the key.

 

[R Henrickson]

A great example of the saying "A picture is worth a thousand words." If the vendors would provide clear photos of their flute shapes it would be simpler.

Especially since companies seem to use the same word to describe different things, and use words with precise meanings (e.g., parabolic) which do not correspond with the actual contours of what they make.

 

[Bill Blasic]

I don't know why your Thompson tool pics of the flute are so shallow as they are not representative of my Thompson tools. Here is a photo of a Robust 5/8" gouge (left) and a Thompson 5/8" gouge (right) and this is what all my Thompson V flutes look like.

 

[Brian Gustin]

the best tool I have used with the Ellsworth grind is the Jamison gouge. for me it performs the flute up shear cut with the leading edge of the wing more Smoothly than any tool I have used.
you call it a vee. Jamieson calls it parabolic. Your diagram confirms vee.
I also heard (reliable source rumor.) that Thompson makes the Jamieson gouge by grinding his 3/4” vee flute in the 5/8” bar..

oddly the 5/8 bar vee from Thompson performed poorly for me with the Ellsworth grind so mine now has the 40/40 and is a nice tool to use with that grind.

the wider flute on the jaimson vee must be the key.

I'm so glad I checked out your reply., I have been saving up for nearly a year for a new bowl gouge and had planned on getting a thompson, as I use the ellsworth grind (and like it) I changed my bookmark (hopefully have enough in my lathe tool account in a couple months) to the Jamieson gouge.. I'd been assuming the Thompson would be suitable for the grind I wanted, but nice to hear from someone who has used both, over relying on the website info.

I agree with Neil, tool vendors should have clear and up to date profile pictures of their tool profiles! (I can't think offhand of a single vendor site I've been to that offers anything other than line drawings of profiles, or "Stock photos" from the web)

 

[robo hippy]

I did see some Jet gouges many years ago that had a V flute that was tighter than the Glaser V, and that Glaser gouge was notorious for clogging up. All of the ellipse/parabolic/catenary type flutes look almost identical to me. I don't need help getting confused! Since I no longer use the swept back grind, I really don't care about specifics of flute shapes other than open V for the 40/40, and a more U or ) shape for my BOB tools.

robo hippy

 

[Karl Best]

As someone who has worked in industry standards development forever, this sounds like something that needs a standard. What is the definition of "parabola", or "V shape", or "U shape", etc. Perhaps AAW could host a discussion among manufacturers, vendors, and resellers and get them to agree on what to call their gouges. If this doesn't work, perhaps the vendors could be encouraged to include end-on photos in their catalogs and on web pages.

 

[henry dalton]

Neil, I really enjoyed and appreciated your article on bowl gouge nomenclature.

 

[Doug Freeman]

Interesting topic Neil. This all agrees with my assessment of the differences in flute shapes. Dwelling on whether the curve is parabolic or elliptical is moot - a parabola is a type of ellipse. Parabolic seems to be the more used terminology these days. Catenary is not a good descriptor.

I agree some standardization in terminology mfrs use would be helpful, as well as actual measurements - actual flute depth (from full circle), for V's actual flute radius and "wall angle", and for parabolics why not publish the equation for the form. The equation is used to machine the tool that cuts the flute, they know what it is (variables within the parabola equation change its shape).

 

[Ron Solfest]

Thanks @Neil S , lots of effort went into this I'm sure. It's clear and well written. I second the comment that this might be a good AAW article.

 

[Neil S]

A great example of the saying "A picture is worth a thousand words." If the vendors would provide clear photos of their flute shapes it would be simpler.

Agreed, Kevin, a 'clear photo' would go a long way to reducing the confusion.

Many makers/vendors provide an oblique view of the tip, which is useful for seeing the grind that will come on the gouge, but a direct end-on view is required to see the actual flute profile. More on that in a following post.

 

[Neil S]

...the best tool I have used with the Ellsworth grind is the Jamison gouge. for me it performs the flute up shear cut with the leading edge of the wing more Smoothly than any tool I have used.
you call it a vee. Jamieson calls it parabolic. Your diagram confirms vee.
I also heard (reliable source rumor.) that Thompson makes the Jamieson gouge by grinding his 3/4” vee flute in the 5/8” bar..

Yes, Lyle writes about the flute on his website as follows...

...it has a better flute configuration—Not a “V”, not a “U” shape — It has a wider, parabolic flute shape than any other gouge made today—The flute change translates into easier, safer, better control.​

But I agree with you, at least on my Jamieson, that it has a V flute that is not parabolic, well not parabolic in the sense that Archimedes, Apollonius, Leonardo da Vinci or Galileo might agree with… :~}

And, yes, the Jamieson is a nicely designed V fluted gouge.

 

[Kent Jaffrey]

Thanks a lot for posting this as it is nice to see pictures to go with the verbal descriptors.

 

[Neil S]

I don't know why your Thompson tool pics of the flute are so shallow as they are not representative of my Thompson tools. Here is a photo of a Robust 5/8" gouge (left) and a Thompson 5/8" gouge (right) and this is what all my Thompson V flutes look like.

Thanks Bill for that photo of the flute on the Robust.

On the apparent shallowness of the V flute on the Thompsons that I have posted compared to the one you have posted, I've found that the orientation at which the end-on photo is taken is important. One of the reasons I didn't include the following photo in my initial posts was that it was taken at a slightly elevated angle to the bottom of the flutes. Unless the sighting is exactly level with the bottom of the flute you start to get a distorted view of the flute profiles...

P&N-Thompson-D-way-Ellsworth
flute profiles
​

As you can see, the view is looking slightly down on, but also slightly sideways on some of the flutes, which distorts the profile. I took that photo back when I was still using fixed handles, thus the placement.

I now use mostly removable handles that allows me to get better side by side photos. I also found that taking the photos at a distance on telescopic reduces parallax foreshortening distortion.

Here are some more photos that I have of my Thompsons...

Thompson 5-8in


Thompson 15v 5-8in


Thompson 3-4in

​

There is some variation there Bill, but overall they are the shallowest bowl gouge flutes I've used. Its small circular radius in the bottom/tip of the flutes is another distinctive feature of Doug's V flutes.

I have a Thompson 3/8" BG for which I might see if I can add a photo of that the next time I am in my workshop.

​

 

[Neil S]

Perhaps AAW could host a discussion among manufacturers, vendors, and resellers and get them to agree on what to call their gouges. If this doesn't work, perhaps the vendors could be encouraged to include end-on photos in their catalogs and on web pages.

I'm not going to hold my breath on getting an agreement among tool makers on that, Karl. But, we can collectively put pressure on both the makers and retailers to provide clear end-on photos to inform our choices and also to avoid the confusion that arises from the sloppy use of descriptors.

Ideally I would like the commonly used descriptors to be as precisely applied as is the heat treatment that all of the mentioned makers use in making their excellent tools. Until then, let's at least have clear end-on photos to see what we are getting.

 

[Russell Nugent]

Great overview.
maybe an article for the AAW journal …
when I took Ellsworth’s class in 1995 we use the Henry Taylor super flute tools. People were calling it parabolic.
the main identifier is the curve in the flute wall. I’ve been using the Ellsworth grind since then and am pretty good with it.

the best tool I have used with the Ellsworth grind is the Jamison gouge. for me it performs the flute up shear cut with the leading edge of the wing more Smoothly than any tool I have used.
you call it a vee. Jamieson calls it parabolic. Your diagram confirms vee.
I also heard (reliable source rumor.) that Thompson makes the Jamieson gouge by grinding his 3/4” vee flute in the 5/8” bar..

oddly the 5/8 bar vee from Thompson performed poorly for me with the Ellsworth grind so mine now has the 40/40 and is a nice tool to use with that grind.

the wider flute on the jaimson vee must be the key.

That is funny. I only have one Thompson tool, the 5/8 V. I've never been able to get it to perform as well as my crappy sheffield Leyland 5/8 V gouges, it just sits there and I wonder what I did wrong to it. Maybe the answer is nothing.

 

[Dennis J Gooding]

It seems to me that this presentation belongs in the Tips and Tutorials Forum

 

[R Henrickson]

It seems to me that this presentation belongs in the Tips and Tutorials Forum

Perhaps, but more people may see and benefit from Neil's work if it remains here.

 

[Neil S]

I have a Thompson 3/8" BG for which I might see if I can add a photo of that the next time I am in my workshop.

​

OK, Bill B, here is my Thompson 3/8" BG and as you can see it also has quite a shallow V flute, relative to its bar size...

​

I took extra care to make sure I was taking that photo in line with the bottom of the flute. Also at a distance but zoomed in to minimise any distortion.

Bill, all of my Thompsons go back at least 12 years, so maybe Doug has changed the depth of his flute grind if yours are more recent (or much older) and deeper. You might also like to check to see if you are looking in line with the bottom of the flutes on yours as that can change the perspective.

 

[Neil S]

It seems to me that this presentation belongs in the Tips and Tutorials Forum

Dennis, I'm comfortable with it here where others can contribute to it and it can be knocked around a bit...

 

[Bill T Tucker]

Thank you for all of the effort...very interesting.
Waiting for your sequel...the different problems encountered in grinding each shape and how to correct
Please!

 

[Russ Braun]

Nice write up, thanks for the effort Neil!

There’s a science to gouges that escapes me. I elected to get a 5/8” gouge to add to my “too many tools” inventory. When getting home, I discovered I now had three identical gouges, two that were allegedly 1/2”. WTH!!

HSS, Powdered Metal and Thompson….I still can only use one at a time!

 

[Doug Freeman]

@Russ Braun are you aware there are 2 different sizing conventions for bowl gouges? US uses shaft dia, Euro uses flute width. If you bought a 1/2” from say Crown, the shaft will be ~5/8”.

 

[Neil S]

I elected to get a 5/8” gouge to add to my “too many tools” inventory. When getting home, I discovered I now had three identical gouges, two that were allegedly 1/2”. WTH!!

Further to Doug's explanation above, in the UK (Sheffield), where most bowl gouges were made for a very long time, the flute width was how they measured the size of a gouge. That was logical as it is the flute that becomes the cutting edge and is that which determines the maximum size of the cut. That convention was established back when gouges were being forged from varying rough stock and the Brits then continued with that convention when they moved over to milling gouges from standard sized HSS round bar.

When turning tool production ramped up in the US the HSS bar stock width from which gouges were being milled became the convention for measuring bowl gouges sizes, as it did down here.

There has always been confusion arising from these two conventions and at times an occasional drift in the convention as applied in the UK (eg. the BGs made for Glenn Lucas by Hamlet in Sheffield are shown as bar sizes).

Because I predate HSS gouges, my preference is for the flute width to be the measure, or for at least the flute and bar width be both stated. However, you have to pick your battles and tightening up on the flute profiles descriptors is more than enough of a challenge for now... :~}

 

[Michael Anderson]

Excellent write up Neil! I appreciate the photos where you isolate the tips of the gouges. Before I realized they were sticking through foam, I thought you bud sacrificed the tips of several of your gouges hahah

 

[Dennis J Gooding]

Dennis, I'm comfortable with it here where others can contribute to it and it can be knocked around a bit...

Neil, you are the boss here. I just think that there is valuable information in your post. It will be effectively lost here in a couple weeks or so.

 

[Neil S]

Waiting for your sequel...the different problems encountered in grinding each shape and how to correct
Please!

Bill

There is much collective expertise about that on this forum, which members are always willing to share. The contribution that hopefully this thread makes is that when we are discussing a particular grind and we say that it is suited to one flute profile or another that we are referring to the same profile. Currently that is not always the case.

 

[Bill Blasic]

OK, Bill B, here is my Thompson 3/8" BG and as you can see it also has quite a shallow V flute, relative to its bar size...

View attachment 49755
​

I took extra care to make sure I was taking that photo in line with the bottom of the flute. Also at a distance but zoomed in to minimise any distortion.

Bill, all of my Thompsons go back at least 12 years, so maybe Doug has changed the depth of his flute grind if yours are more recent (or much older) and deeper. You might also like to check to see if you are looking in line with the bottom of the flutes on yours as that can change the perspective.

Neil I have a lot of Thompson tools and I went through all the drawers and I found tools just like what you are showing and the fact that most I have do look like your photo (and they could be possibly be up to 18 years old ) . The ones I use look like my photo but due to the fact that I probably will never wear out the ones I am using due to CBN wheels I never have occasion to look in those drawers. Perhaps I am using the 5/8 Deep Flute Bowl Gouge and the Jimmy Clewes 1/2" and 3/8" gouges which are cut deeper, don't know? I will put my grind on one of the tools with the flute you are showing and see what it looks like. This is what my 5/8" gouge I use looks like (this may not be my photo but it is representative of my grind). I have been around Doug since the beginning and have worked in the booth for many years but this year at Louisville will be my last in the booth so if you go stop by and say hello!

 

[Oliver Moss]

Fantastic post and information, thank you for it!

 

[RichColvin]

I think that this discussion is quite important, so I added a link to it on the Sharpening Handbook.

 

[Marc Banka]

Adding a few photos of gouges not covered thus far.
First is a Carter & sons 5/8 deep fluted bowl gouge. A U-shaped flute. I find the transition from the round bottom to the straight cut upper difficult to have a grind without a bump. Certainly takes care.

Second is a Oneway master cut 5/8 bowl gouge. Looks elliptical to me, also deep and wide. I love this with a 40-40 style grind. My workhorse.